An epidemic of laughter

Consider the extraordinary 1962 outbreak of contagious laughter in a girls' boarding school in Tanzania. The first symptoms appeared on January 30, when three girls got the giggles and couldn't stop laughing. The symptoms quickly spread to 95 students, forcing the school to close on March 18. The girls sent home from the school were vectors for the further spread of the epidemic. Related outbreaks occurred in other schools in Central Africa and spread like wildfire, ceasing two-and-a-half years later and afflicting nearly 1,000 people.